In many fields, the angular orientation of a body (e.g., the rotational orientation or "roll" of the body relative to some reference plane) must be determined. This determination may be needed to permit the body to be guided or directed towards a desired destination or simply to permit the orientation of the body to be known, controlled or varied as desired. In many cases, the determination must be made while the body is moving along a velocity vector in object space--within a six degree of freedom spatial model. Various systems for determining the angular orientation of a moving body are known, however each of these systems suffers from at least one of several inherent problems.
For example, an electrostatic/electromagnetic roll reference sensor is known which can be used to determine a vertical reference (relative to the plane of gravity) for a spin-stabilized projectile moving in object space. See, e.g., U.S. Pat. No. 4,328,938 to Reisman et al. which discloses such a sensor. In addition, antenna systems which transmit varying signals to ground-based equipment can be used to calculate projectile roll. See, e.g., U.S. Pat. No. 5,372,334 to Cuadros. Similarly, gyroscopes which can be used to determine vertical are also known. See, e.g., U.S. Pat. No. 4,297,905 to Hadekel. Finally, various needle-and-ball, pendulum, radar/barometric altimeter, and aircraft-type wing attitude devices are known.
Each of the aforementioned devices, however, suffers from specific problems. For example, the Reisman roll reference sensor requires complex support circuitry and further requires that the body be moving along a spin-stabilized trajectory. Moreover, the system must be reconfigured for use in different hemispheres. Similarly, the Cuadros antenna system requires a complex ground-based transceiver, requires that the body be spin-stabilized and will only operate in line-of-sight applications. The Hadekel gyroscopic system requires an expensive, complex gyroscope and support componentry.
The remaining systems suffer from similar complexity, cost and/or technical problems.
What is needed, therefore, is a simple, rugged, inexpensive angular reference system which can be used to determine the roll orientation of a body moving in object space. Ideally, the system should be operable anywhere and under any conditions from low g's launch to, for example, cannon launched and anywhere around or about the planet earth and even within other gravitational networks, should operate beyond the horizon, and should operate regardless of whether the body is rotating with an angular velocity (either natural or induced).